Corrosion inhibitors



Patented Feb. 24, 1953 CORROSION INHIBITORS Carl F. Prutton, New York, N. Y., assignor to The Lubrizol Corporation, Wickliffe, Ohio, at corporation of Ohio No Drawing. Application September 2, 1949, Serial No. 113,909

9 Claims.

This application is a continuation-in-part of my copending application, Serial No. 671,123, filed May 20, 1946, now abandoned, which in turn was a continuationeiivpart of my then copending application, Serial No. 369,227, filed December 9, now Patent No. 2,400,573, dated May 21, 1946'; which application was a continuation-inpart of my then copending application Serial No. 99,165, filed September 2, 1936, now abandoned.

The present invention relates to the art of treating metal and is particularly directed to an improved method of the treatment of metal surfaces to prevent corrosion and rust.

Many attempts are known in the prior art to provide rust and corrosion inhibitors for metals, but these efforts heretofore have either proved unsatisfactory or too expensive in practice to warrant their wide commercial adoption.

In general, objects of this invention are to provide a coating composition which is very stable in its use and application; one that is usable for metals directly without preliminary treatment or finishing operations; a compound which is inexpensive and generally reduces the cost of coating metal.

The specific object hereof is to provide a compound which will react with the metal to which it is applied to eiiiciently protect the surface of such metal and effectively prevent oxidation and corrosion.

In accordance with the present invention, I have discovered that certain phosphorus-containing compounds, generally known as the phosphide compounds, in non-aqueous media are readily applicable to metal surfaces to inhibit corrosion action. More particularly, this invention is concerned with organic phosphide types of com-' pounds containing a metal group, and still more specifically the organo-metallic phosphides. For most purposes, it is preferred to employ an organmmetallic phosphide of such nature that in contact with an aqueous media they will yield a solution having a pH of below about 7, my research and tests showing the most satisfactory results to be when the'pI-I is between about 4 and 6, in most cases. For reasons not too clearly understood the organo-metallic phosphides give particularly good results in inhibiting corrosion of such metals as for example ferrous types, hear: ing metals of copper-lead, cadmium-silver, or analogous types.

For the purposes of this specification and the appended claims, the term organo metallic phosphide is intended to include those compounds in which the metal substituent is solely attached to 5 preference.

2' I the phosphorus atom, and such compounds must contain at least one organic radical attached to the phosphorus atom.

Generally, the organo-metallic phosphides can be represented by the following structural formula:

( a) MaPbRc where M is a mono-, dior pclyvalent metal, R is an organic radicle, hydrogen, or halogen, at least one of which is an organic radicle, and a and b can be eitiher one or two, and 0 can be up to 4:, depending on the valence of the. metal.

divalent metal, a is 1, b can be either 1 or 2,' and 0 can be either 1 or 4, in accordance with- To illustrate this point, when M is a the following subgeneric structural formulae:

The organo-metallic. phosphides can have present therein metals from groups I and II of the periodic system, namely the alkali or alkaline earth metals. Other p'olyvalent metals also can be suitably employed,'however, itis referable to use metals from groups I and H of the periodic system. Q

The halogen present in the phosphides of this invention generally can be of any halogen, but it is preferred to'employ chlorine as the halogen contained in theorgano-metallic phosphides.

The organic radicles as previously mentioned can be one or more Rfs in the generic structural'Forinula (a) given hereinabove. In a more particular identification of the types of organic radicles present in thegorgano metallic phosphides, the table below enumerates examples thereof in an order of convenience rather than It is preferred to employ oil solu- TABLE I Organic radicles radicles enumerated under I and IV. Halogen bearing radicles The halogen, for example chlorine, can be present in any of the organic radicles listed under I, II, and III above.

Examples of organo-metallic phosphides found applicable for the purposes of this invention in elude:

Calcium amyl phosphide Barium octyl phosphide Zinc octyl phosphide Barium cresyl phosphide.

Barium benzyl phosphide Magnesium chlorophenyl phosphide Phenyl lead phosphide It is not to be inferred that all organo-metallic phosphides are equivalent in efiicacy, but that under certain conditions some organo-metallic phosphides are more desirable than others.

In order that a better understanding can be obtained of my invention, two illustrative examples of methods of preparation will be given. It should be understood that the examples are given by wayof illustration and not by way of limitation.

An organic phosphine which may be either RPFIZ or RQPH is reacted with an alkali metal such as sodium or potassium to produce a phosphide. The alkali metal is dissolved in liquid ammonia. The alkali dissolves in liquid am monia without reaction. The organic phosphine is then introduced slowly into the solution.

When using an organic phosphine of the,

formula RPH2 and when using equal molecular portions of the organic phosphine and metal there will be produced a compound having the formula RPHM. However, when 1 mol of the organic phosphine RPI-Iz is combined with 2 mols of the metal, a phosphide having the formula RPMz is produced. When utilizing an organic phcsphine of the formula RzPH, 1 mol thereof will be used for a mol of metal and the phosphide produced will have the formula RaPM.

A second method for the preparation of the phosphides is by means of the reaction of an organic phosphine with zinc diethyl. Accordingly, to this method an organic phosphine of the formula RPHz is introduced to the liquid zinc diethyl and. at room temperature or only slightly above room t emperature the reaction will proceed to the production of n P-ZnP ethane When using an organic phosphine of the formula RzPH the reaction thereof with zinc diethyl will result in the following:

+ ethane A further advantage of the present discovery in the compatibility of certain organo-metallic phosphides in relatively pure state with oils and with vehicles used in coating materials, such as paints, varnishes, lacquers; and with other solvents partly or wholly immiscible with water. This is especially valuable in carrying out the invention as the corrosion inhibiting compound may be included in ornamental or preservative coating mixtures and applied to the surface to be treated without an extra operation. Still further, it has been found that the afiinity of organometallic phcsphide compounds with paint, varnish, and lacquer coating materials generally improves the resulting coating and provides an effective bond or adherence thereof to the surface of the metal due to the reaction of such compounds with the metal.

In practice, a metal surface may be treated with an organo-metallic phosphide in an oil or other carrying vehicle to provide a thin coating on such, surface. One very effective method comprises heating a coating liquid to a suitable temperature, immersing the article to be protected, and then Cooling or drying in air the thin adherent coating upon the article which resulted from the bath. The drying may be accelerate-:1 by placing the coated article in a suitable oven.

The novel coating compound is preferably carried in non-aqueous media, such as petroleum oils and solvents, fatty oils, greases, waxes, or other organic solvents, or mixtures of the above such as are used as vehicles for paints, varnishes, lacquers, etc. Such compound will then react by itself or in contact with water or with the surface of the metal to which the coating is, applied, to produce thereon a protective coating. It has been found that certain of these organo-metallic phosphides will attack the metal and produce a roughening of the metal and thereby greatly increase the adherent properties of such metal when an ornamental coating is applied thereto.

The invention also contemplatesphysically combining with the organo-metallic phosphidc. an organic derivative of an inorganic acid, e. g.

In the following table re listed specific aamples of types of sulphonic acids, esters and TABLE II Sulphonic acids, e. g.:

Benzene sulphonic acid Naphthalene sulphonic acid Amyl naphthalene sulphonic acid Capryl benzene sulphonic acid Lauryl benzene sulphonic acid Lauryl sulphonic acid Cetyl sulphonic acid Petroleum mahogany sulphonic acids Esters of sulphonic acids, e. g.:

Butyl ester of benzene sulphonic acid Benzyl ester of benzene sulphonic acid Chlor-benzyl ester of benzene sulphonic acid Phenyl ester of lauryl sulphonic acid Ethyl ester of cetyl sulphonic acid Phenyl ester of petroleum mahogany sulphonic acid Salts of sulphonic acids, e. g.:

Calcium salt of petroleum mahogany sulphonic acid Barium salt of petroleum mahogany sulphonic acid Magnesium salt of petroleum mahogany sulphonic acid Aniline salt of petroleum mahogany sulphonic acid Calcium salt of lauryl benzene sulphonic acid Zinc salt of capryl benzene sulphonic acid From the foregoing it will be observed that the particular derivatives of sulphuric acid listed are characterized by the formula Where M is hydrogen (acids), an organic radicle (esters) or a metal (salts).

Other specific examples of the above mentioned organic derivatives of inorganic acids are:

Ethyl silicates Ethyl sulphuric acid Lauryl sulphuric acid Aniline sulphate An example of the combination of one of the 7 above with an acid compound of phosphorus is: Sulphonated diphenyl phosphoric acid.

It is very important to note that the processes involving the admixture of the novel inhibiting compound with another coating composition provides a more satisfactory bond or means of attachment of such other composition to metal surfaces. Obviously, if an ingredient of a coating composition does in itself react with and adhere to a metal surface, then such composition carrying this ingredient will become permanently adhered to the metal when applied.

As an example of a composition Which may be employed for the purposes of the present invention, calicum amyl phosphide may be employed in combination with the calcium salt of petroleum mahogany sulphonic acid in a non-aqueous oil vehicle.

As stated in the general outline of this invention, it is sometimes desirable that organo-metallic phosphides to be used as the present novel inhibitor be of such nature that in contact with water they will yield a solution having a pH of below 7, preferably below 6 and above 4. Such materials are of sufficiently acidic nature as to react chemically with metal surfaces to form ad herent protective coatings.

Because of the very nature of the organometallic phosphides it has been found that such agents as moisture, which ordinarily promotes corrosion, will, when attacking the metal surface treated by the present novel coatingmethod, produce an accelerated reaction of such organometallic phosphides used in the coating with the metal to form a thin protective layer.

While I have presented theories to explain the action of organo-metallic phosphides as corrosion inhibitors, it should be understood that I do not intend to be bound thereby. The theories have been solely presented with the view of aiding the advancement of the arts as much as possible.

From the above description, it has been shown that the compounds described, when incorporated in a coating composition, are all effective and desirable corrosion and oxidation inhibitors.

The present invention is not limited to the specific embodiments of the present invention and not limitations of the scope thereof. Likewise the quantities of materials employed and the procedure of preparation may be widely varied without departing from the scope of this invention, nor is it intended to limit the use of any member of the new class of inhibitors to any particular coating composition. The present invention is limited solely by the claims attached as a part of this specification.

The amount of the above-described organometallic phosphides required for my purpose depends upon the nature of the compound, the kind of use, and the character of the vehicle. In the case of certain of the more active compounds, a very low percentage is sufficient, e. g. from 0.01 to 0.25%, and for most purposes, amounts up to about 5% are desirable. Usually only a minor amount need be used; but in the case of certain of the materials, for example, particularly those useful as pigments or fillers much higher proportions, up to or more, may be found useful.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A corrosion inhibitor for metal surfaces comprising the combination of an oil-soluble organo-metallic phosphide; which compound has a metal substituent solely attached to phosphorus and contains at least one organic radical selected from the class consisting of hydrocarbon and halogen-containing hydrocarbon radicals, and a non-aqueous oil vehicle.

2. The corrosion inhibitor of claim 1 is further characterized by yielding a pH value below '7 when in contact with an aqueous media.

3. A corrosion inhibitor for metal surfaces comprising the combination of an oil-soluble organo-metallic phosphide compound having the general formula MdPlbRc wherein M is a metal solely attached to P and R is selected from the group consisting of hydrogen, halogen, hydrocarbon, and halogen-containing hydrocarbon radicals having a valence of one, which compound contains at least one organic radical; a and b can be either one or two, and c is not less than one or more than four, such compound when in contact with an aqueous media yields a soluwherein M is a bivalent metal and R. is a hydrocarbon group having valence of one, which compound upon contact with an aqueous media yields a solution having a pH of below '7; and a nonaqueous oil vehicle.

7. A corrosion inhibitor for metal surfaces comprising in combination (a) an oil-soluble organo-metallic phosphide, which compound has a metal substituent solely attached to phosporous and contains at least one organic radical selected from the class consisting of hydrocarbon and halogen-containing hydrocarbon radicals, and upon contact with an aqueous media yields a solution having a pH of below 7; (b) an organic compound selected from the group consisting of organic sulphonic acids, esters of organic sulphonic acids, and salts of organic sulphonic acids; and (c) a non-aqueous oil vehicle.

8. A corrosion inhibitor for metal surfaces comprising in combination (a) calcium amyl phosphide, and (b) a non-aqueous oil vehicle.

9. A corrosion inhibitor for metal surfaces comprising in combination (a) calcium amyl phosphide, (1)) calcium salt of petroleum mahogany sulphonic acid, and (c) a non-aqueous oil vehicle.

CARL F. PRUTTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,149,271 Butz Mar. 7, 1939 2,199,944 Van Peski et al. May '7, 1940 2,224,695 Prutton Dec. 10, 1940 2,321,307 Mikeska et a1. June 8, 1943 2,340,331 Knutson et a1 Feb. 1, 1944 2,400,573 Prutton May 21, 1946 2,486,664 Marling et al. Nov. 1, 1949 FOREIGN PATENTS Number Country Date 483,400 Great Britain Apr. 20, 1938 

1. A CORROSION INHIBITOR FOR METAL SURFACES COMPRISING THE COMBINATION OF AN OIL-SOLUBLE ORGANO-METALLIC PHOSPHIDE, WHICH COMPOUND HAS A METAL SUBSTITUENT SOLELY ATTACHED TO PHOSPHORUS AND CONTAINS AT LEAST ONE ORGANIC RADICAL SELECTED FROM THE CLASS CONSISTING OF HYDROCARBON AND HALOGEN-CONTAINING HYDROCARBON RADICALS, AND A NON-AQUEOUS OIL VEHICLE. 